Precision resistor



March I, 1949. s. A. -HOLMQVIST 2,463,384

PREcIsioN RESISTOR Filed Jan. 27, 1947 Eli/79.7 .RR 5 RN- I 3 *flu-mr'uunmmw 112/11 ezvbcz JZAJETO lJIL/ZU i161 Patented Mar. 1, 1949 PRECISION RESISTOR Seth August Holmqvist, Appelviken, Sweden, as-

signor to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a company of Sweden Application January 27, 1947, Serial No. 724,627 In Sweden February 18, 1946 8 Claims. 1

The invention refers to precision resistors provided with potential-terminals. The manufacturing of precision resistors, also includes an adjustment of each resistor in order to ascertain the resistor having the proper resistance value. Said adjustment, hitherto being a very tedious work, is often performed by successively removing small portions of the resistance, wire until the resistance, with the desired degree of accuracy, has the proper value. My invention intends to produce such a resistor, at which the work necessary for the adjustment is considerably simplified. The invention is characterized by one of the ends of the resistor being connected to one end of an adjusting resistor, the value of which is 0.1 to 0.001 of the value of the first mentioned resistor, and by an adjustable contact member, connected to one of the terminals of potential of the precision resistor, being arranged to be set in an arbitrary position along the adjusting resistor and possibly to be locked in set position.

The invention will be described more closely with reference to the accompanying drawing, in which Fig. 1 is a wiring diagram showing an adjustable precision resistor consisting of ten resistor units with a switch arranged for connexion of an arbitrary number of said units and with auxiliary circuits necessary for the adjustment of said units. Fig. 2 shows an application of the invention to a fixed resistor. On the drawing, I, 2-H] indicate the different resistor units, H, i2, it etc. indicate outstretched resistance wires, each being connected between two units following each other, l5, l6, l1 etc. indicate the sliding contacts, which can be moved along the pertaining resistance wires ll, l2, l3 etc., and which are connected through wires 33, 34, 35 etc. to contacts 2!, 22, 23 of the switch, the turnable arm of which is indicated by 3 1. One end of the resistor unit 4 is connected over wire 32 to contact 20 and to potential terminal Kl and the turnable 3? is connected to potential terminal K2. The same end of said resistor unit is also connected to current terminal K3, and one end of resistance wire is is connected to current ter minal K4. On adjustment, a circuit comprising the variable resistance RR, a source of current B a standard resistor RN are connected to the terminals K3, K4, said standard resistance RN moreover being connected by its ends over line L to contacts 4|, 43 of a switch A, connected to a compensator K, shown on the drawing as a Dubois Raymond compensator. The terminals K! and K2 are connected to the contacts Ml, 4-2

of the switch A, compensator K may, by means of switch A, be connected alternately to terminals Kl, K2 or resistor RN. The compensator being known per se consists of a battery E, an adjustable resistor RD, a sliding contact S and a galvanometer G. The resistance of the standard resistor RN is suitably chosen equal to the desired resistance of each of the resistor units l-Hl. Supposing that the resistor unit l is to be adjusted, the current intensity through resistor units !-l [i and standard resistor RN is first regulated by means of resistor RR to suitable value, whereupon the position of sliding contact 3 along resistor RD is regulated until the galvanometer G shows 0. During this, the arms A of the switch must rest on contacts 4|, 43. The arms A of the switch are thereafter moved to contacts 40, 42 and sliding contact I5 is moved along wire H until the galvanometer shows 0. It is then ascertained, that the resistance of the resistor unit 1' plus the resistance in wire ll right to sliding contact l5 equals the resistance of standard resistor RN, the resistance of resistor unit 1 thereby being adjusted to its proper value. The sliding contact is locked in the set position, e. g. by means of a screw, which may possibly be sealed. The turnable arm 3l must rest on contact 2! during said measurements. If resistance unit 2 is thereafter to be adjusted, contact 2! is connected to potential terminal Kl, the connection between contact 20 and terminal Kl thereby being broken. The arm 3! is then turned so as to rest on contact 22. The measurements described in connection with the adjustment of resist-or unit I are now repeated, the resistance value of resistor unit 2 thereby also being adjusted. In the same way, the resistance value of the other resistor units 3-H) can also be ad justed. If any of the resistor units is to be given a resistance value differing from the value of the other units, standard resistor RN may naturally, on adjustment of said unit, be changed for a resistor, the value of which equals the value of the desired resistance of said unit. Instead of the shown compensator K any other compensator may naturally be used. It is also possible, when adjusting, to use another method of comparison, in which method the resistance over e. g. resistor unit I and that part of wire ll, being connected to said unit, and being limited by sliding contact i5, is. compared to some known resistor. The resistance value of the adjusting wire, e. g. H, must naturally be considerably lower than the resistance value of resistor unit I, and the relation between first mentioned and last mentioned J3 resistance value will be dependent on the desired accuracy of adjustment. For the greatest accuracy occurring in the practice, said relation should be ca. 0.001 whilst said relation should be ca. 0.1 by the lowest accuracy occurring in the practice. The resistance of the adjusting wires by unity of length is also suited to the desired accuracy of adjustment. When a great accuracy of adjustment .is desired, a certain displacement of the sliding contact along the wire must give a relatively small difierence of the resistance, and in said case the resistance of the adjusting wire per unity of length should then be low.

The rheostat shown in Fig. 1 contains ten'resistor units. The number of resistor units may naturally be arbitrary. In case it is desired to adjust only one fixed precision resistor, only one adjusting wire is needed. Fig. 2 shows how the resistors will in said case be connected to the terminals KlK i. The resistance wires ll, l2 etc. shown in Fig. l to be straight, outstretched wires, may naturally also be arranged along an arc, the sliding contacts Hi, It etc., thereby being arranged on a turnable arm. Instead of a single wire, a coilwound wire known per se in rheostats may be used.

The invention is naturally not limited to the embodiments shown above, but can be modified in several different ways within the scope of the idea of the invention.

I claimf 1. Precision resistor provided with two current terminals and two potential terminals and comprising a main resistor and an auxiliary resistor, said resistors being connected in series, the resistance' value of said auxiliary resistor being 0.1 to 0.001 of the resistance value of said main resistor, the free end of said main resistor being connected to one of said current terminals one of said potential terminals being connected to a point on said main resistor and the free end of said auxiliary resistor being connected to the secondof said current terminals, and an adjustable contact member being designed to be set in an arbitrary position along said auxiliary resistor and beingconnected to the second of said potential terminals.

2. Precision resistor provided with two-current terminals and two potential terminals and comprising a number of part resistors, said part resisters being connected in series, each part resistor consisting of a main and an auxiliary resistor, said last mentioned two resistors being connected in series, the resistance value of each of said auxiliary resistor being 0.1 to 0.001 of the resistance value of said belonging main resistor, an adjustable contact member for each of said auxiliary resistors, each of said contact members being designed to be set in an arbitrary position along the belonging auxiliary resistor, and to be connected'to an appertaining contact in a switching device designed to connect an arbitrary of said last mentioned contacts to one of said potenresistor being connected to one of said current terminals one of said potential terminals being connected to a point on said main resistor, and the free end of the last of said part resistors being connected to the second of said current terminals.

3. Resistor according to claim 2, wherein each of said auxiliary resistors consists of an outstretched resistance wire.

4. Resistor according to claim 2, wherein each of said auxiliary resistors consists of a coilwound wire.

5. Resistor according to claim 2, wherein each of said adjustable contact members is designed to be locked in set position.

6. Resistor according to claim 1, wherein said auxiliary resistor consists of an outstretched resistance wire.

7. Resistor according to claim 1, wherein said auxiliary resistor consists of a coilwound wire.

.8. Resistor according to claim 1, wherein said adjustable contact member is designed to be locked in set position.

SETH AUGUST HOLMQVIST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,997,164 .Zuschlag Apr. 9, 1935 FOREIGN PATENTS Number Country Date 196,613 Great Britain Apr. 18, 1923 

